Hello all,

We pretty much tried to solve the same issue here with a new API in DMA-IOMMU:

Christopher- the user part would be MFC devices on exynos platforms

On 9/23/20, Christoph Hellwig <h...@lst.de> wrote:
> On Wed, Sep 23, 2020 at 08:48:26AM +0200, Marek Szyprowski wrote:
>> Hi Shaik,
>> I've run into similar problem while adapting S5P-MFC and Exynos4-IS
>> drivers for generic IOMMU-DMA framework. Here is my first solution:
>> https://lore.kernel.org/linux-samsung-soc/20200918144833.14618-1-m.szyprow...@samsung.com/T/
>> It allows to remap given buffer at the specific IOVA address, although
>> it doesn't guarantee that those specific addresses won't be later used
>> by the IOVA allocator. Probably it would make sense to add an API for
>> generic IOMMU-DMA framework to mark the given IOVA range as
>> reserved/unused to protect them.
> If you want to use IOVA addresses in a device otherwise managed by
> dma-iommu we need to expose an API through the dma API.  Can you please
> include the iommu list in the discussion of your series?
> I don't think using the raw IOMMU API is a very idea in these drivers,
> we probably want a way to change the allocator algorithm or hint the
> next IOVA and keep using the normal DMA API.  Maybe Robin has a better
> idea.
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